The establishment and persistence of bacterial microcommunities may be dependent on specific interactions between different organisms that inhabit the microcommunity. Dental plaque represents one such microcommunity, which is characterized by a complex and highly organized set of interactions among oral bacteria as well as between bacteria and human oral tissue. Coaggregations, microbial cell-to-cell interactions among genetically distinct partner strains, are mediated by complementary cell surface components on the participating bacterial partners. An extension of this idea is that bacteria also may recognize host epithelial cells by some of these same surface components. The overall focus of this project is to investigate cell adherence molecules, cell signaling molecules, gene expression and gene transfer among bacteria within human oral biofilms and to relate these events to the architecture of the bacterial biofilm community. Our aim is to understand the molecular mechanisms of cellular communication and their relationship to the development and establishment of subgingival plaque and colonization of the host epithelial cells.